The aim of study was to study about the mechanisms of redistribution of fetal circulation. Animal experiments were performed with goat fetuses which were incubated using an extrauterine incubation system with arteriovenous extracorporeal membrane oxygenation. The effects of changes in fetal PaCO2 on circulatory functions were assessed. The hypercapnea was induced gradually by decreasing the flow of gas to the membrane oxygenator located on the extracorporeal circulation system. The fetal carotid arterial blood flow increased significantly due to the hypercapnea. Although a slight increase was observed in the heart rate at the mild hypercapnea stage, severe hypercapnea induced bradycardia in all cases. We found that cerebral blood flow increased due to hypercapnea's direct effect on the vascular system, but the response of the peripheral chemoreceptor to hypercapnea seemed to be attenuated in chronic stimulation.The effects of changes in fetoplacental circulation on the central nervous system (CNS) of premature fetuses were studies. Stress experiments to cause ischemia and reperfusion to the CNS were performed with 5 goat fetuses maintained in the extrauterine incubation system. Coagulation necrosis, which correspond to an initial lesion of periventricular leucomalacia could be observed in deep white matter of the brain in 3 out of 5 fetuses. We also found that disturbance of feto-placental circulation may cause an adverse effect in the CNS of premature fetuses.また臍帯静脈に送血する体外循環回路の閉鎖・開放を繰り返すことにより、虚血・再潅流モデルを作製し、胎児・胎盤循環の変動が中枢神経におよぼす影響に関して検討した。5例の子宮外保育中のヤギ胎仔に負荷実験を行ったところ、3例に脳室周囲の深部大脳白質に限局性の凝固壊死巣を認めた。この病変は、脳室周囲白質軟化症(PVL)の初期病変に一致しており、脳血流の自動制御能が未熟な未熟ヤギ胎仔胎仔では、臍帯循環の変動に伴って中枢神経系の虚血・再潅流が発生し、PVLが発生する可能性があることが明らかとなった。